The present invention relates generally to an adaptor for increasing the amount of task light available from portable table and floor harp system lamps now in service to offset the natural deterioration of eyesight with age.
More specifically, the present invention relates to an adaptor for the manual conversion of in-service portable floor and table harp system lamps from (a) a single female Edison screw socket adapted to receive an Edison-based, base-down, incandescent, compact florescent or LED light bulb to (b) a plural down-socket LED lighting system with materially increased and better task lighting, where the rapid conversion does not require any special skills or the use of tools, does not require any modification of the wiring of the conventional lamp, and does not change the aesthetics of the lamp.
Harp System Lamps.
It has been estimated that that there are over 500 million portable table and floor lamps in service in the United States and Canada, in homes, apartments, dormitories, offices, hotels, etc. Portable lamps have a base adapted to rest on a horizontal surface, a decorative cored body, and a decorative shade. While such lamps are generally purchased to provide light, the selection of the lamp actually purchased is almost entirely architectural, i.e., on the basis of the appearance of the lamp body and its shade. Lamp aesthetics is thus critical and includes, e.g., the relationship of the size and shape of the body and shade, the height of the lamp source within the shade, and the absence of glare from the light source. The space available under the shade for the light source is restricted by safety considerations and the necessity [of] for avoiding visual “hot spots” on the shade due to proximity to the light source. These aesthetic requirements lead almost universally to the use of a “saddle” supported at the junction of the base and the single up-socket to support a “harp” which in turn supports the shade in the desired location relative to the lamp body and keeps the shade from contacting the light source. Both the nature and the amount of light available from such “Harp System Lamps” is provided by the lamp owner's choice of the bulb installed in the single up-socket.
As shown in the prior art FIG. 1, the typical Harp System Lamp may include an ornamental base 10 from which the electric power cord 12 extends to an electrical receptacle in the wall or floor. An ornamental body 14 cored for the passage of the electrical wiring of the lamp extends upwardly from the base 10 to an upwardly opening Edison screw socket 16 (an “up-socket”) for a base-down Edison based bulb 18. The up-socket 16 may include a simple on/off switch 26 but is often a “3-way” socket, i.e., a four position switch that may be manually toggled from an “off” position through a “low” and a “medium” to a “high” light position in which an additional light source such as an additional incandescent filament within the same bulb is energized to provide more light.
A saddle 20 located just below the up-socket 16 removably receives the bottom ends of the legs of a harp 22 that extends upwardly on both sides of the socket 16, bending radially outward around the light source 18 to provide a support for the lamp shade 24 as well as preventing contact of the shade with a bulb 18 in the socket 16. The harp 22 supports the shade 24 at the desired height relative to the lamp body 14 and a finial 23 is used to retain the shade on the harp 22.
The shade 24 laterally surrounds the socket 16 and bulb 18 to diffuse the light and reduce glare. The shade may be in the form of a cylinder (i.e., a “drum” shade), a truncated cone or pyramid, an oval, a rectangle, or a square. While some light may pass through the shade 24, the shade defines openings at the top and the shade is generally reflective. The light emitted by the bulb 18 is generally horizontally omni-directional and the shade 24 is generally shaped to reflect light through the top opening as area light and through the bottom opening as task light.
The light source 18 historically is a single incandescent bulb received in the up-socket 16. Because the light source is base-down and relatively low in elevation, upright stability for the Harp System Lamp is easily designed into the lamp by the weight and footprint of the base 10.
Adequacy of Available Task Light.
A “lumen” is a measurement of the amount of light produced and a “foot-candle” is a measurement of the light intensity at some defined point. Lumens are thus generally used to indicate the total light output of the light source, and foot-candles are generally used to measure the brightness of the light illuminating a particular workspace or desktop.
Harp System Lamps require a shade to prevent glare and only a very small percentage of the light impinging on the shade passes through it. With common shades, about 25-35 percent of the lumens emitted by the light source pass out of the opening at the top of the shade to be reflected off the room ceiling to provide indirect area light. About 20% of the lumens are absorbed within the shade or are transmitted horizontally through the material of the shade. In general, only about 50% of the total lumens emitted by a base-down bulb exit the opening at the bottom of the shade 24 as task light, with about a third of those lumens provided only when the shape and material of the shade directs light impinging on the shade toward the task area. Despite the small proportion of the total lumens available as task light, Harp System Lamps are widely used as task lights, i.e., to read magazines or newspapers, to do needlework, to play cards, to work with a computer, etc.
Industry sources suggest that 150 to 500 foot candles are needed to perform tasks such as reading, with the difficulty of the task, the age of the person performing the task, and the length of time the task is performed being contributing factors.
The adequacy of the available task light from Harp System Lamps for a specific task is determined by the person using the lamp and there are three factors contributing significantly to that determination for most Harp System Lamp users.
One factor is the base down orientation of the light source in Harp System Lamps. Tests were conducted with a Harp System Lamp having an 9 inch harp and an common ivory translucent “Empire” shade having a 13″ top and a 17″ bottom, providing a 10″ slant height shade sloped at about 20 degrees to the vertical.
With a 60 w incandescent base-down bulb in the Harp System Lamp up-socket, a horizontal task surface was selected about 16.5″ below the top of the socket at a radial distance of about 12.5″ as the test “Task Site”. The light measured on the Test Site was about 22 foot-candles. Even with the historic but now disfavored 100 w incandescent bulb base-down in the Harp System Lamp, the task light on the Task Site was only about 42 foot-candles, i.e. less than half of the minimum foot candles recommended for reading.
A second factor is age. The number of people in the United States age 50 and older has, in the last 30 years, increased to 100 Million and the median age of the population has increased from 33 years to 38 years. People need more light as they age, it being well understood in the medical and scientific communities that people age 50-60 need three times the light they needed in adolescence. People naturally lose about 65% of their visual acuity between age 20 and 60 in addition to developing visual impairments such as presbyopia, macular degeneration, cataracts, and glaucoma. This is the natural deterioration of eyesight with age, and suggests that a mature reader needs at least double the recommended foot candles.
A third factor is a long standing government energy conversation policy encouraging the replacement of incandescent light bulbs with “lumen equivalent” LED and CFL bulbs which last for many years and use less energy, but provide significantly less task light in table and floor lamps.
For example, an incandescent bulb produces 1600 lumens for 100 w, a CFL bulb produces 1600 lumens for 23-28 w, and an LED bulb produces 1600 lumens for 15-20 w. Efforts to match the horizontal “omni-directional” nature of incandescent bulbs have resulted in coiled “compact” or “CFL” fluorescent bulbs and in arrays of light emitting diodes or “LEDs”. Such retrofit bulbs substantially outlast incandescent bulbs of the same total lumen output, but generally double the price to the consumer.
Equivalent CFL and LED bulbs are generally sold only by comparison with the total light output from incandescent bulbs, i.e., as “total lumen equivalent” bulbs. For example, a 23 w CFL and a 15 w LED bulb are sold as “equivalent” to a 100 w incandescent bulb. All three bulbs produce a total of about 1600 lumens, but the light emitted from CFL and LED bulbs is asymmetrical when compared to an incandescent bulb, with the light from LED bulbs, depending on the manufacturer, being even more asymmetrical than CFL bulbs because the LEDs themselves are highly directional. Tests show that a significant portion of task light from a lamp using retrofit bulbs is lost to the consumer because of the squelching necessary to diffuse and spread the light from such inherently asymmetrical sources.
Additional tests with the Harp System Lamp referenced supra and a 60 w equivalent CFL base-down bulb (14 w) in the Harp System Lamp socket, the light at the Test Site was measured at about 16 foot-candles as compared with the 22 foot-candles from the 60 w incandescent bulb. With a 100 w equivalent CFL bulb (23 w), the light at the Test Site was measured at about 34 foot-candles as compared with the 42 foot-candles from a 100 w incandescent bulb. Thus, the use of base-down retrofit florescent bulbs in a Harp System Lamp significantly reduces the available task light and is well below the recommended level.
The test results for lumen equivalent LED bulbs are similar. For example, a typical 100 w equivalent LED bulb (15 w) in a base-down configuration produces only 36 foot-candles as compared with the 42 foot-candles from a 100 w incandescent bulb. Thus, the use of base-down retrofit LED bulbs in a Harp System Lamp is also well below the recommended level.